(1) Field of the Invention
The present invention relates to image forming apparatuses such as printers and copiers, and particularly relates to technology for controlling switching to a sleep mode, in which power supply to parts of an image forming apparatus that consume a large amount of power is limited to be a low level or is stopped, in order to reduce the power consumption by the image forming apparatus.
(2) Related Art
Image forming apparatuses, such as printers and copiers, are not always used continuously, and the frequency of use varies according to the time of day. For this reason, image forming apparatuses are generally enabled to switch to a power save mode (i.e. a sleep mode) for a period in which they are not in use, in order to reduce the power consumption during the period. In the sleep mode, power supply to the parts that consume a large amount of power (e.g. an image formation section that includes a fixing device, a photoreceptor, a developer, and the likes) is stopped, and the image forming apparatus in the sleep mode can not perform image formation operations.
As an example of such image forming apparatuses, there is an image forming apparatus that is capable of scheduling switching to the sleep mode so that the image forming apparatus can switch to the sleep mode after completion of a print job (See Japanese Patent Application Publication No. 2006-184541). Due to the scheduling, the image forming apparatus can easily switch to the sleep mode after the completion of a print job. Consequently, the power consumption during a period in which the image forming apparatus is not in use can be reduced.
However, even if it is shortly after the image forming apparatus has switched to the sleep mode, the sleep mode will be cancelled when an event that requests for cancellation of the sleep mode occurs (e.g., in the case where a print job has been scheduled and has been input to the apparatus with designation of a start time of the job). This means that the sleep mode will be canceled before the effect of the sleep mode is fully achieved, and, on the contrary, the power consumption could be increased in some cases due to a warm-up operation, which is performed to return to a standby mode (i.e. a mode in which the apparatus can start an image formation operation immediately), and consumes a certain amount of power.